// Copyright (c) 2019-2020 Alexander Medvednikov. All rights reserved.
// Use of this source code is governed by an MIT license
// that can be found in the LICENSE file.
// SHA512 block step.
// This is the generic version with no architecture optimizations.
// In its own file so that an architecture
// optimized verision can be substituted
module sha512

import math.bits

const (
	_k = [u64(0x428a2f98d728ae22),
		  u64(0x7137449123ef65cd),
		  u64(0xb5c0fbcfec4d3b2f),
		  u64(0xe9b5dba58189dbbc),
		  u64(0x3956c25bf348b538),
		  u64(0x59f111f1b605d019),
		  u64(0x923f82a4af194f9b),
		  u64(0xab1c5ed5da6d8118),
		  u64(0xd807aa98a3030242),
		  u64(0x12835b0145706fbe),
		  u64(0x243185be4ee4b28c),
		  u64(0x550c7dc3d5ffb4e2),
		  u64(0x72be5d74f27b896f),
		  u64(0x80deb1fe3b1696b1),
		  u64(0x9bdc06a725c71235),
		  u64(0xc19bf174cf692694),
		  u64(0xe49b69c19ef14ad2),
		  u64(0xefbe4786384f25e3),
		  u64(0x0fc19dc68b8cd5b5),
		  u64(0x240ca1cc77ac9c65),
		  u64(0x2de92c6f592b0275),
		  u64(0x4a7484aa6ea6e483),
		  u64(0x5cb0a9dcbd41fbd4),
		  u64(0x76f988da831153b5),
		  u64(0x983e5152ee66dfab),
		  u64(0xa831c66d2db43210),
		  u64(0xb00327c898fb213f),
		  u64(0xbf597fc7beef0ee4),
		  u64(0xc6e00bf33da88fc2),
		  u64(0xd5a79147930aa725),
		  u64(0x06ca6351e003826f),
		  u64(0x142929670a0e6e70),
		  u64(0x27b70a8546d22ffc),
		  u64(0x2e1b21385c26c926),
		  u64(0x4d2c6dfc5ac42aed),
		  u64(0x53380d139d95b3df),
		  u64(0x650a73548baf63de),
		  u64(0x766a0abb3c77b2a8),
		  u64(0x81c2c92e47edaee6),
		  u64(0x92722c851482353b),
		  u64(0xa2bfe8a14cf10364),
		  u64(0xa81a664bbc423001),
		  u64(0xc24b8b70d0f89791),
		  u64(0xc76c51a30654be30),
		  u64(0xd192e819d6ef5218),
		  u64(0xd69906245565a910),
		  u64(0xf40e35855771202a),
		  u64(0x106aa07032bbd1b8),
		  u64(0x19a4c116b8d2d0c8),
		  u64(0x1e376c085141ab53),
	 	  u64(0x2748774cdf8eeb99),
		  u64(0x34b0bcb5e19b48a8),
		  u64(0x391c0cb3c5c95a63),
		  u64(0x4ed8aa4ae3418acb),
		  u64(0x5b9cca4f7763e373),
		  u64(0x682e6ff3d6b2b8a3),
	 	  u64(0x748f82ee5defb2fc),
		  u64(0x78a5636f43172f60),
		  u64(0x84c87814a1f0ab72),
		  u64(0x8cc702081a6439ec),
		  u64(0x90befffa23631e28),
		  u64(0xa4506cebde82bde9),
		  u64(0xbef9a3f7b2c67915),
		  u64(0xc67178f2e372532b),
		  u64(0xca273eceea26619c),
		  u64(0xd186b8c721c0c207),
		  u64(0xeada7dd6cde0eb1e),
		  u64(0xf57d4f7fee6ed178),
		  u64(0x06f067aa72176fba),
		  u64(0x0a637dc5a2c898a6),
		  u64(0x113f9804bef90dae),
		  u64(0x1b710b35131c471b),
		  u64(0x28db77f523047d84),
		  u64(0x32caab7b40c72493),
		  u64(0x3c9ebe0a15c9bebc),
		  u64(0x431d67c49c100d4c),
		  u64(0x4cc5d4becb3e42b6),
		  u64(0x597f299cfc657e2a),
		  u64(0x5fcb6fab3ad6faec),
		  u64(0x6c44198c4a475817),
	]
)

fn block_generic(dig mut Digest, p_ []byte) {
	mut p := p_
	mut w := [u64(0)].repeat(80)
	mut h0 := dig.h[0]
	mut h1 := dig.h[1]
	mut h2 := dig.h[2]
	mut h3 := dig.h[3]
	mut h4 := dig.h[4]
	mut h5 := dig.h[5]
	mut h6 := dig.h[6]
	mut h7 := dig.h[7]
	for p.len >= chunk {
		for i in 0..16 {
			j := i * 8
			w[i] = (u64(p[j])<<56) | (u64(p[j + 1])<<48) | (u64(p[j + 2])<<40) | (u64(p[j + 3])<<32) | (u64(p[j + 4])<<24) | (u64(p[j + 5])<<16) | (u64(p[j + 6])<<8) | u64(p[j + 7])
		}
		for i := 16; i < 80; i++ {
			v1 := w[i - 2]
			t1 := bits.rotate_left_64(v1, -19) ^ bits.rotate_left_64(v1, -61) ^ (v1>>6)
			v2 := w[i - 15]
			t2 := bits.rotate_left_64(v2, -1) ^ bits.rotate_left_64(v2, -8) ^ (v2>>7)
			w[i] = t1 + w[i - 7] + t2 + w[i - 16]
		}
		mut a := h0
		mut b := h1
		mut c := h2
		mut d := h3
		mut e := h4
		mut f := h5
		mut g := h6
		mut h := h7
		for i in 0..80 {
			t1 := h + (bits.rotate_left_64(e, -14) ^ bits.rotate_left_64(e, -18) ^ bits.rotate_left_64(e, -41)) + ((e & f) ^ (~e & g)) + _k[i] + w[i]
			t2 := (bits.rotate_left_64(a, -28) ^ bits.rotate_left_64(a, -34) ^ bits.rotate_left_64(a, -39)) + ((a & b) ^ (a & c) ^ (b & c))
			h = g
			g = f
			f = e
			e = d + t1
			d = c
			c = b
			b = a
			a = t1 + t2
		}
		h0 += a
		h1 += b
		h2 += c
		h3 += d
		h4 += e
		h5 += f
		h6 += g
		h7 += h
		if chunk >= p.len {
			p = []
		}
		else {
			p = p[chunk..]
		}
	}
	dig.h[0] = h0
	dig.h[1] = h1
	dig.h[2] = h2
	dig.h[3] = h3
	dig.h[4] = h4
	dig.h[5] = h5
	dig.h[6] = h6
	dig.h[7] = h7
}

